My Super cool predictions for the final war are:
At some point some really bad shit gonna get out about the World Government, its gonna be something like the origional 20 founders, were actually pirate crews (This will potentially happen after Luffy finds the one piece, and the truth is revealed then? Maybe this is what roger was laughing at? idk)
This is gonna cause the World Government to fracture into two halves, Koby Garp Fujitora on one side, Akainu Greenbull ect on the other (We already seeing this somewhat happen with sword and the admirals leaving)
This is basically gonna cause a power vacuum since the Navy would be at its weakest
Blackbeard gonna take advantage of this, and try take over the Navy to put himself as king of the world
This will lead to Shanks getting involved somehow? (Shanks dies here?)
The Fractured Navy allies with the RA?
Basically an all out war, Blackbeard vs Navy vs RA vs Straw hats vs Kaido (dude aint dead) basically everyone all trying to get out on top achieving their own thing
At some point Luffy gonna destroy the read line, This would cause Fishman island to be destroyed aswell (Already seen in a prophecy) would cause Laboon to stop bashing his head against the terracore wall, and would also destroy Marijois (So destroying both the bottom and top of the world, both physically and symbolically) which would then be a symbol for a more equal era
End of my super cool theory